Oracle10g Developer: PL/SQL Programming 1

Objectives

Programming fundamentals The PL/SQL block Define and declare variables Initialize variables The NOT NULL & CONSTANT variable options Perform calculations with variables SQL single-row functions in PL/SQL statements Decision structures: IF-THEN and CASE Looping actions SQL*Plus bind variables

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Program Logic Flow

Identify sequence of actions needed prior to coding Use a flowchart to visually represent the sequence of

actions

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Flowchart - Search for Coffee Products

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Decision Structures

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Looping Structures

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PL/SQL Blocks

What is a block? What are the different segments of a block? How does data get into a block? How are different data types handled?

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Brewbean’s Challenge

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PL/SQL Block Structure

DECLARE – create variables, cursors, and types BEGIN – SQL, logic, loops, assignment statements EXCEPTION – error handling END – close the block

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Variable Names

Begin with alpha character Up to 30 characters Can contain upper and lowercase letters, numbers, _

, $ , #

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Scalar Variable Data Types

Character – CHAR(n)

VARCHAR2(n) Numeric – NUMBER(p,s) Date – DATE Boolean – BOOLEAN (T/F)

Note: Only holds a single value

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Example Scalar Declarations

DECLARE lv_ord_date DATE; lv_last_txt VARCHAR2(25); lv_qty_num NUMBER(2); lv_shipflag_bln BOOLEAN;BEGIN ---- PL/SQL executable statements ----END;  Note: Minimum requirements are variable name and data type

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Test Variables

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Variable Initialization

•Set a variable value when the variable is created

DECLARE lv_ord_date DATE := SYSDATE; lv_last_txt VARCHAR2(25) := 'Unknown'; lv_qty_num NUMBER(2) := 0; lv_shipflag_bln BOOLEAN := 'FALSE';BEGIN ---- PL/SQL executable statements ----END;

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Test Variable Initialization

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Variable Declaration Options

NOT NULL – the variable must always contain a value CONSTANT – the variable value can not be changed in

the block

DECLARE

lv_shipcntry_txt VARCHAR2(15) NOT NULL := 'US';

lv_taxrate_num CONSTANT NUMBER(2,2) := .06;

BEGIN

---- PL/SQL executable statements ----

END;

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Calculations with Scalar Variables

multiplication

DECLARE lv_taxrate_num CONSTANT NUMBER(2,2) := .06; lv_total_num NUMBER(6,2) := 50; lv_taxamt_num NUMBER(4,2);BEGIN lv_taxamt_num := lv_total_num * lv_taxrate_num; DBMS_OUTPUT.PUT_LINE(lv_taxamt_num);END;/

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Using SQL Functions

•SQL functions such as MONTHS_BETWEEN can be used within PL/SQL statements

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Decision Structures

Control which statements in a PL/SQL block will execute

Enables conditions to be tested to determine the flow of statement execution

Most programming languages provide IF and CASE statements to enable conditional processing

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IF Statements– Simple IF– IF/THEN/ELSE– IF/THEN/ELSIF/ELSE

CASE Statements– Basic CASE statement– Searched CASE statement– CASE expression

Decision Structures

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Simple IF Statement

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IF/THEN/ELSE

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IF/THEN/ELSIF/ELSE

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Logical Operators within IF

Logical operators (AND, OR) enable multiple conditions to be checked

IF lv_state_txt = 'VA' OR lv_state_txt = 'PA' THEN

lv_tax_num := lv_sub_num * .06;

ELSE

lv_tax_num := lv_sub_num * .04;

END IF;

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Basic CASE Statement

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Searched CASE

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CASE Expression

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Looping

Enables a statement or set of statements to be executed more than once

A loop must provide instructions of when to end the looping, or an ‘infinite’ loop will be produced

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Basic LOOP

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WHILE Loop

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FOR Loop

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Host/Bind Variables Declare

Using application environment variables to send variables into and out of a PL/SQL block

SQL*Plus is an application environment

BEGIN

:g_state_txt := 'VA';

END;

/

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Using Host/Bind Variables

DECLARE lv_tax_num NUMBER(4,2); lv_sub_num NUMBER(6,2) := 100;BEGIN IF :g_state_txt = 'VA' THEN lv_tax_num := lv_sub_num * .06; ELSIF :g_state_txt = 'CA' THEN lv_tax_num := lv_sub_num * .08; ELSE lv_tax_num := lv_sub_num * .04; END IF; DBMS_OUTPUT.PUT_LINE(lv_tax_num);END;/

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Summary

A flowchart assists in laying out processing logic A PL/SQL block contains a DECLARE, BEGIN,

EXCEPTION, and END sections Variables to hold values are declared Scalar variables hold a single data value Scalar variables can hold string values, numbers,

dates, and Boolean values DBMS_OUTPUT.PUT_LINE is used to display

values

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Summary

IF statement structure is IF/THEN/ELSIF/ELSE CASE statements provide decision processing

similar to IF statements Looping structures include: basic, WHILE, and FOR Host or bind variables can be used to interact with

the application environment